Generally, when an electronic component is mounted on a printed board, cream solder is firstly printed on the electrode pattern arranged on the printed board. This cream solder printing is carried out by screen printing using a metal screen in which a multiplicity of holes has been formed corresponding to the electrode pattern. The electronic component is provisionally fixed to the printed board printed with the cream solder by the viscosity of this cream solder. Moreover, the electronic component generally is provided with a multiplicity of electrodes and leads, and these electrodes and leads are bonded to their corresponding respective cream solders. That is, a single electronic component is mounted on a group of solders formed from a multiplicity of cream solders. Moreover, after mounting of the electronic component, this printed board is brought to a reflow furnace, and soldering is performed by passage through a certain reflow process. At the stage prior to the reflow process (prior to mounting of the electronic component), the cream solder is inspected, and inspection is performed to determine whether or not the electronic component is loaded properly for the stage after passage through the reflow furnace.
Conventionally, due to the occurrence of time-wise expansion and contraction or due to errors during production of the metal screen and the like, the cream solder can be printed at a position that is shifted from the electrode pattern. In such a case, there are instances of placement of the cream solder with almost no shifting on the electrode pattern when going through the above-mentioned reflow process. This is due to the cream solder melted during the reflow process and operating by spreading across and wetting the electrode pattern face (self alignment effect) due to the reflow process. Here, technology is proposed (e.g., see Patent Citation 1 and the like) when the self alignment effect is anticipated that mounts the electronic component by shifting the electronic component by just the degree of shift or direction of shift when the degree of shift or direction of shift is nearly fixed for various cream solders used for mounting one electronic component, even when the cream solder is printed at a somewhat shifted position.
However, during inspection of cream solder during the stage prior to the reflow process, inspection is based on whether or not the shift amount of the actually printed cream solder is within a previously set range value relative to the ideal cream solder printing position. However, the cream solder positional shift amount during inspection prior to reflow is large, and even through a determination of “failure” may be made, there are instances when a “pass” determination is made after the reflow process due to the previously mentioned self alignment effect. However, when the positional shift of each solder is relatively small, even though a determination of “good” is made during inspection prior to the reflow process, when there is variance in the positional direction of the various solders, the electrodes and the like of the electronic component cannot be loaded on the cream solder, and as a result, there is concern that a “failure” determination may result at the inspection after the reflow process. That is, there is concern that the results of inspection will become different for the inspection prior to the reflow process versus the inspection after the reflow process.
Consistency should be achieved between the inspection result prior to the reflow process versus the inspection result after the reflow process, and technology has been proposed (see Patent Citation 2 and the like) that makes various types of alterations to the above-mentioned value range that becomes the determination standard of positional shift amount of the cream solder prior to the reflow process. This technology will be explained in detail. When an item determined to be a “failure” during the inspection prior to the reflow process is determined to be a “good” item during inspection after the reflow process, the above-mentioned value range is determined to be excessively narrow, and the value range is made wider than it had been previously. However, when an item determined to be “good” during inspection prior to the reflow process is determined to be a “failure” during inspection after the reflow process, the above-mentioned value range is determined to be excessively wide, and the value range is made narrower than it had been previously.    [Patent Citation 1] Unexamined Laid-open Patent Application No. 2002-84097    [Patent Citation 2] Unexamined Laid-open Patent Application No. 2006-37236